Advice about Microwaving

Archived Responses: 

Does microwaving really do something bad to the food?

Dec 2004

I know some people don't like to use microwaves, but I'm not entirely sure why that is. Does anyone have any concrete evidence of microwave dangers? I mean, does it really do anything bad to the food? Thanks JLY

This was sent around on the Web: Dr. Edward Fujimoto, manager of the Wellness Program at Castle Hospital, was on TV talking about dioxins and how bad they are for us. He said that we should not be heating fatty foods in the microwave using plastic containers. He said that the combination of fat, high heat and plastics releases dioxin into the food and ultimately into the cells of the body. Dioxin are carcinogens and highly toxic. Instead, he recommends using glass, Corning Ware, or ceramic containers for heating food. So such things as TV dinners, instant ramen and soups, etc., should be removed from the container and heated in something else. Paper isn't bad but you don't know what is in the paper. To add to this: saran wrap placed over foods as they are nuked, with the high heat, actually drips poisonous toxins into the food. Don't freeze your plastic water bottles with water as this also releases dioxin in the plastic. peg
I received yesterday a mail from a friend warning about the dangers of microwaving food in a plastic container: the process would release carcinogenic substances in the food! Being my paranoid self I made my soup-in-a-bowl lunch in a ceramic plate instead of the provided plastic container, and last night when my son wanted to defrost meat that was in a foam receptacle I told him to use a glassware instead. It would be interesting to find out if there are any solid evidence to this! paranoid mum
This is a well-known urban legend, based on a small amount of facts. See: That site also lists what the USDA says to do, which can basically be summed up to: Only use cookware that is specially manufactured for use in the microwave oven. These can be glass, ceramic, paper, and plastics as long as they're labeled for microwave oven use. These are all tested and rated to safely endure the heat of foods being cooked in/on them from a microwave. Other items may not be and can actually start to melt, which is when stuff in the plastics could become mixed with your food. Mike
Please note that the thing about dioxins leaching into plastic from microwave use appears on my favorite web page for checking out urban legends --, as basically false, at least in the form it appeared in several of the posts in the last advice column. Check out I make it a policy, anytime I hear anything alarmist like this, ESPECIALLY in the form ''I heard it in an email from a friend...'', to check it out on snopes before passing it on. Karen
Snopes has a full account of this story - although I would be careful about what kinds of plastics you use in the microwave, the information being sent around via email is not founded in any real studies:

By the way - Snopes is an excellent resource for testing the veracity of urban legends. I'd suggest ALWAYS checking before mass-forwarding email pronouncements that you receive. jean

Um, that e-mail about plastics dripping toxins into our food in the microwave -- that's been largely discredited by the American Cancer Society. See lastic.asp?sitearea=MED and We should really try not to believe every piece of e-mail we receive. Wendy
I'd heard this then heard it was a hoax. You can check out the full skinny at (almost always good for this sort of rumor mill stuff, like the deodorant/cancer ''link''). Interesting reading. Merrilee
The bit about microwaving food in plastic container is false - http:// (actually is really good for checking any kind of info like that... although pretty much as a rule I would not believe 99% of information that comes through an email forward.) just the facts!
I Googled this topic and found several urban legend/rumor type sites partly debunking this message; see

which links to the Dept. of Agriculture guidelines on microwaving safely:

The dioxins thing isn't a hoax but - well, judge for yourself... Corliss

Do not believe these stories. I am an anlytical chemist and specialize in analyzing food packaging materials and their migration or lack of into foods. I have extensive experince in the testing of all manners of food packaging materials and can guarantee that no dioxins or other poisonous toxins are present in the food packaging materials and cannot be released or dripped into the food. Brad Brad
Claim: Research shows that microwaving foods in plastic containers releases cancer-causing agents into the foods.

Status: False

See for full text.

Summary below:
Origins: This ''health alert'' began appearing in people's inboxes in February 2002; It's a pretty good assumption that if using plastic containers in microwaves \x97 as millions of people have been doing for decades \x97 posed a significant risk of cancer, you'd be hearing about it somewhere other than an e-mail forward. Is there really something to the central claim of this e-mail, that heating plastic in microwaves releases a cancer-causing agent into the food? It's within the realm of possibility, but it must be stressed the FDA does impose stringent regulations on plastics meant for microwaving. Also, if there are dioxins lurking in the plastic containers we heat food in and the process of warming those receptacles looses those nasties into our ingestibles, we've yet to locate the studies that prove this. However, because most dioxins are dangerous compounds we want to have as little to do with as possible, many people are cautious about using anything associated with them. So, if you're one of the concerned, be sure that when you cover a dish you intend to microwave with ordinary plastic wrap you do not let the covering touch the food, because some of the plasticizer in the wrap \x97 which may contain toxic chemicals, as opposed to does contain toxic chemicals \x97 could migrate to what you're cooking, especially foods high in fat. Alternatively, use waxed paper for this purpose. Those who are very, very cautious about the potential for dioxin contamination might choose to adopt the central point of the e-mail's advice, which is to decant all items into glass or ceramic containers before microwaving. But how real is this concern? According to Dr. George Pauli, a leading Food and Drug Administration scientist, not very. He acknowledged that some plasticizers do migrate into foods, particularly those containing a lot of fat, oil, or sugars. But research has found no ill effects from consumption of plasticizers in FDA-approved plastic wraps or from freezing or re-using plastic water bottles. Even so, others remain unconvinced, and those on both sides of the issue recommend not letting plastic wrap touch food during microwaving.

In the few posts I read in response to this question, posters referred to information they received via email or on the web about the possible dangers of microwaving food in plastic containers and using saran wrap in the microwave, etc.

So many of these emails that get passed around are made up and an excellent site to look at before you pass these emails or the information in them on to anyone is They research these e-rumours and publish what they find out.

Here is a link to their report on the email about microwaves and plastic. They found it to be ''unproven & fiction'' but interested folks should read the report itself as you may consider it more ''disputed'' than ''fiction'' and the report also provides links to where to find more accurate information on this issue: is also a great site to look up any other ''urgent,'' ''important,'' or other mass emails that you receive. Whitney

Microwaving Baby Food

March 2002

Does anyone have any information on heating up frozen cubes of baby food in the microwave? Is there a problem with killing the nutrients in the organic food that I prepare? I usually use the defrost level three for two minutes. Any advice would be appreciated. Dawn

The nutrients in any kind of food are sometimes changed by cooking and preparing... check out the book Super Baby Food by Ruth Yaron. It's all about making, freezing and serving homemade baby food. There is some information there about microwave usage for this. I also make and serve organic, frozen baby food to my son. I do not have a microwave, so we get the next day's food out of the freezer the night before and it thaws overnight in the fridge. Then we put the containers in a hot water bath for about ten minutes prior to feeding time. This works great! -Laura
Freezing food and then defrosting it with a microwave will ensure the food loses a lot of its vitality. Freshly cooked food would be better and can be stored in a sealed container in a refrigerator for about 3 days. Microwaves are not advisable for heating or cooking any food. Mary.
I don't know about killing the nutrients but I microwave the cubes of babyfood all of the time. I put the cubes in a bowl and set the microwave for between 30 and 45 sec. I stir and then put back in for another 15 or so depending on the number of cubes and what type of food it is. I can't wait to see other people's responses. Joelle

Microwaving Formula

March 2002

Is it OK to use the microwave to warm up my baby's bottle? I have heard conflicting information as to whether the only risk is hotspots, which can be managed by diligent shaking, or whether the microwave actually changes the nutritional value of the formula or breast milk. Thanks for any info.

I've always been told that microwaving formula and/or breastmilk is a bigno-no. I believe it breaks down the composition of the milks. But I learned a trick from the neonatal intensive care unit for heating up milk: Microwave a cup of water for 1-1/2 minutes. (The hospital used foam coffee cops; I used coffee mugs.) Then put the bottle of formula or breastmilk in the hot water for about 30 seconds. Gwynne
Microwaving breatmilk is a HUGE no-no. There are living anti-bodies in breastmilk, and they die in the microwaving. Though you can always micro-wave water, and use that hot water to thaw frozen milk, or warm cold milk. There are fairly inexpensive bottlewarmers that you can buy too. I heard about someone taking her frozen bags of milk, and using the coffee maker to thaw it. I'm not exactly sure what she did though. Microwaving formula, as I understand it, you only risk hot-spots. Though if you're worried about it, just heat the water, and add the formula to that. The hot water helps disolve the formula better anyway!
To be safe, I used to microwave the water (eg. in a big mug) before adding it to the baby's bottle with the formula powder. But, if your baby's like mine, you may find that s/he doesn't really care whether the formula's heated or not! - Mom of a 6-mo. old
Here's what has worked for us: Breast milk: to heat this up we microwaved half a mug of water for about 45 seconds. We set the bottle in the mug of warm water and the breast milk was warmed up in about 3 minutes. It worked well for us to get the bottle started then change baby's diaper. By the time our routine was finished, the milk was warmed. Formula: We microwave the bottle with 4-6 oz. of cooled boiled water for 10-15 secs. and add formula after that. We don't put the nipple in the microwave and have never experienced any hot spots on the bottle (and we Also, another suggestion: Someone gave us an Avent Bottle Warmer. It plugs in, warms the water very quickly and you can set the bottle (formula or breast milk) in to warm up. It takes a little longer than the suggestions above but, the advantage about this is that it comes with a bowl that sitson top of the steamer (obviously not at the same time a bottle is warming). You can put baby food in the bowl and it will warm it up but it takes 10-15 mins. to heat a jar of food that Linnea
My son has been on formula since birth. What I do when I make his bottle is microwave the water in the bottle before I add the formula, when making a single bottle. But when you want to make a few bottles ahead of time, just shake them up and remove the nipple before microwaving. I have also asked around about whether or not the nutrition level is lowered after microwaving bottles and the only warning I have heard is that hot spots in the bottle can form. I personally have never had that problem just do not microwave the bottle more than 15 to 20 seconds on high. My son is 20lbs now and perfectly healthy. Good luck! Alex
I'm replying because someone just wrote that she ''couldn't wait'' to see responses to her post! I also microwave frozen cubes for my 1 year old boy. I'm a very lazy cook, and while I like to get as much nourishing food as possible for my baby, I HATE the process of cooking it and preparing it into baby food edibles. I really am much less likely to do it if it means 3X daily [or more!]. So we do a bunch ahead of time, freeze it, then microwave it for 20-30 seconds to get it mildly warm. Mmmm, organic veggies come pre-chopped in bags! Whole Foods has frozen organic sweet potato cubes! Soy nuggets, boca burgers, home-made soups! He loves them all, and I'm actually feeding him healthy foods, which, believe me, I'm much less likely to be vigilant about if it means lots of extra time at the stove. Which, by the way, means less time with him on the floor. anonymous
I found the microwave discussion interesting. I did a Google search and found a site called ''How Things Work,'' by a physics professor, Louis A. Bloomfield, at the University of Virginia It is done in question and answer form, and he will answer your questions. He explains how microwaves work, addresses the perceived dangers of microwaves, and discusses whether microwaves have an affect on the nutritional value in food. His answer,'' No more so than conventional heating does. Overheating some nutrients can damage them, so that microwave cooking does affect food's nutritional value. But microwave cooking is far less likely to cause serious molecular damage to food than flame broiling or frying.'' I hope this helps. Julie

Plastic and microwaves

Nov 2002

I've heard that microwaving food in plastic containers is somehow harmful, but I don't have any more information than that. Does anybody have any information they can share? Is it a particular type of plastic? Does it matter what kind of food? What about baby bottles? Thanks Jill

An alternative to using plastic wrap in the microwaves is to cover your food with a wet paper towel. Wax paper would work also but doesn't cling as well. Trish
Putting plastic in the microwave is bad for the air. Some people say that you shouldn't even have plastic in the house. Plastics release volatile organic compounds. The more flexible it is, the worse it is. For instance, the plastic they wrap around meat is probably one of the worst. The hard plastic that encases your tv is probably one of the best. This website has information on indoor air pollution and putting plastics in the microwave: You can get thousands of web pages by typing ''sick building syndrome'' ''environmental illness'' ''multiple chemical sensitivity'' or ''indoor air pollution'' into a search engine. Some are personal web pages. Some is research done by NASA or the EPA. There is plenty of information out there for people who want to improve their health. Indoor air pollution can cause cancer many years down the line. But it can also affect almost any body system immediately: skin, lungs, digestion, central nervous system, emotions, etc. sunsol
I asked your question to Paul Goettlich of, and got an extensive list of studies mostly having to do with plastic itself leaching into the food it holds. He did have some studies about microwaving plastics that will answer your question. Here's what he sent me:

Microwaving plastics: Plastics for microwaving can be made of various types of polymers. Food wrap is generally made from PVC, especially the commercial brands that come in large sizes from food supply companies. Consumer brands are also made of PVC, but some are being made of other types.

When reading the files below, please understand that the literature on the toxicity of plastics is not only limited, but the bulk of it does not take into account the extremely low concentrations that have an effect on the endocrine system. Nor do they account for the synergy that can occur between any number of chemicals/polymers. Additionally, each person is unique and in their own unique environment.

Here are a few file for you to read:
How Plastics Are Made Microwave enhances overall migration from PVC to foods Packag. Technol. Sci. 12, 277-281. Polyethylene Terephthalate Migration and Toxicity Evaluation of plastics for food packaging Food Additives and Contaminants v.11, n.2, 221-230 1994 Detecting Nonylphenol in PVC Food Wrap Japan Offspring Fund (JOF) Monthly Newsletter n.117 & 118 Feb99 Plastic food wrap poses threat to environment: Dioxin TADASHI MATSUI & YOMIURI SHIMBUN / The Daily Yomiuri (Tokyo) 15feb00 Does Plastic in Microwave Pose Health Problems? Wall Street Journal 12oct98 is a great site for finding out information on plastics and other toxic things in our environment. Every time I go to this site and read something, I look around and realize how much plastic is in my own home. Then I go to the store and realize how few alternatives we have to it these days. Check it out! Melissa

I read a study somewhere done by a teenager about the use of plastic in microwaves and its dangers. Her findings were widely accepted. She found that the fat in the food that is microwaved causes a chemical reaction with the plastic container that is not healthy. The recommendation was to to put the food to be microwaved in a glass container. The less the fat in the product the lesser the chemical breakdown withthe plastic. yancy
I'm so glad you asked about this! It's something I feel very strongly about.

My understanding about plastics is that certain kinds of plastics can essentially off-gas chemicals into the foods that are stored in them. Some of these chemicals are carcinogenic, and some of them are what are called ''Endocrine Disrupting Chemicals'' (EDCs), which cause reproductive system harm. This means that many of the compounds (from what I understand) can emulate oestregens, and that causes, well...this is what an article in the Green Guide says:

''...scientists hypothesize that endocrine-disrupting (hormone-altering) chemicals that we encounter in our everyday lives, such as in the food we eat, may be responsible for the dramatic decline in sperm counts and increasing rates of breast, testicular and prostate cancers, endometriosis, and some birth abnormalities, such as undescended testicles. In wildlife, endocrine disrupting chemicals have been linked to abnormal reproductive organs in Florida alligators and compromised immune systems in dolphins.''

Here are some tips:
- Plastic wrap should never come in contact with fatty food in the microwave. It is also important not to use left-over margarine or yogurt tubs in the microwave. Use ceramic or glass cookware instead.
- Avoid food, water and beverages sold in cans, plastic containers and bottles, when possible. Try to buy water from distributors who can deliver large glass jugs in convenient dispensers.
- As a precaution, you can unwrap prepackaged foods and store them in nontoxic glass, ceramic or steel bowls, or Ziploc bags (made of LDPE).
- In general, heat promotes leaching.

Mothers and Others (also in the Green Guide) have a great guide about food storage containers, which I've included:

Plastic used for containers can be identified by their recycling codes, as listed below. Most wraps on pre-packaged foods lack identifying symbols [so assume they are not good for the microwave]:

1. Polyethylene Terephthalate (PETE or PET): No known hazards.

2. High Density Polyethylene (HDPE): No known hazards.

3. Polyvinyl Chloride (PVC or vinyl): Plasticizers are added to many PVC products to make them flexible. These include phthalates -- suspected endocrine-disrupting chemicals (EDCs), DEHA, another possible EDC, was found to leach from PVC cling wraps into cheese. Grocery stores commonly use PVC to wrap deli meats and cheeses. Reynolds cling wrap is PVC. Some waters and vegetable oils are bottled in PVC. Ad PVC's manufacture and incineration produces highly toxic dioxins, as does the PVDC used in Saran Wrap, according to Consumers Union.

4. Low Density Polyethylene (LDPE): No known hazards.

5. Polypropylene (PP): No known hazards.

6. Polystyrene (PS or Styrofoam): Made from styrene, a suspected carcinogen, PS also contains p-nonylphenol; both chemicals are suspected EDCs. Do not consumer fatty foods or alcoholic beverages from Styrofoam containers; styrene can leach into these substances. Some opaque plastic cutlery is PS, as well.

7. Other Resins, including Polycarbonate (PC): Most clear plastic baby bottles and 5-gallon water bottles are made of PC. Bisphenol-A EDC is in PC, and has been found in water and heated infant formulas bottles in PC, as well as food cans lined with a plastic film.

I got this from ''The Green Guide'' newsletter, which is a really great source for ''practical everyday actions benefiting environmental and personal health''. I have found more excellent information from them about pesticides, drugs, and so on than anywhere else. If you are interested in subscribing (which I recommend for any parent), they are at: Heather

Avent plastic bottles safe for microwaving?

Nov 2002

In the same vein as the 'plastic and microwaves' subject (see below) ...does anyone know if the avent bottle system has PVCs? Are avent bottles safe for microwaving milk/soy milk/formula in? I have been unsuccessful at locating any info on these bottles both on the web and Consumer Reports. Maya

I did a great deal of research on Avent bottles in 2000 and found very little information. In the end, I was left with the conclusion that the verdict is still out on microwaving ANY plastics and I thus got into the habit of microwaving a Pyrex glass measuring cup of water and plopping my bottle in it for a few minutes. It takes just a few minutes longer than microwaving the bottle itself, but I figured it was safe and would also avoid any ''hot spots'' that would occur by microwaving the milk directly.

On the same note, I found some cute little glass Pyrex dishes at Safeway and I use them everyday to microwave food (instead of plastic refrigerator containers).

Good luck with your decision. Mom of two

I don't know about PVC in the plastic, but I used to microwave water in the Avent bottle, then add formula. They are advertised as microwave safe, - but another issue came up. The plastic would expand, making it near impossible to screw the nipples so they popped in just right. This meant a lot of leaks would occur. When the plastic is cool, it was easy to screw the nipple in right even if the formula was hot. Just something to consider if you need to place nipple on right after microwaving. marian
Avent bottles contain Bisphenol-A, an endocrine disrupting chemical. (If you want to know why those are to be avoided, read Our Stolen Future or check out the website I would recommend switching to glass bottles, and -- if you have to use plastic -- using bottles that are not clear plastic, like the Avent ones. But, hey, you asked about microwaving. Heating plastics increases the amount of leaching that occurs, so I would definitely avoid it. Judith
The instructions with Avent bottles indicate that the bottle (but not the nipples, spouts, etc.) are safe in the microwave. Liz O.
Avent bottles are polycarbonate. Their liners are polyethylene. Search for ''bisphenol'' and you'll find the relevant articles to baby bottle safety. The plastics industry and FDA refute Consumer Report's allegations though:

PVC, otherwise known as vinyl, is softened with plasticizers that leech out over time (vinyl gets brittle). It's carcinogenic, etc. It's mostly used in teether toys and Saran wrap.

Polycarbonate, when heated, supposedly leeches bisphenol-A, which acts like estrogen hormone and disrupts glands.

Elsewhere, I've heard that microwaves drive minute plastic particles into food as well as potentially alters the chemistry/nutrition of food.

I'm practical rather than paranoid: I err on the side of caution if I can afford to. I microwave food in glass, then transfer it to the serving container, use Glad Cling Wrap (polyethelene) instead of Saran, etc.

Here's my non-polycarbonate, non-microwave solution: I keep a large vacuum-insulated bottle which I fill up every morning with boiling water. When I need to warm a baby bottle, I dispense hot water into my 32 oz tumbler and dunk my Avent liner bottle into it. It's ready to serve in 5-10 mins. Kim

i believe avent bottles are polycarbonate, not pvc, but also these are not good for kids. medela, evenflo colored and opaque (not clear), and gerber (colored) are all made out of #5 for recycling (PP), which is ok. they might have changed, i have an old list from ''mothers and others'' which might be outdated now (their web site is gone for some reason). in recycling code, apparently you want to avoid not only #3 (pvc) but also #6 (PS) and #7 (polycarbonate). often you have to call the manufacturer and they can tell you (not always, someone from lamaze told me that their toy was safe, after days of trying to get info, ''because it is made of plastic'').... and maybe mothers and others are more cautious than you want to be.... joanne
I would urge you not to microwave any bottle filled with breastmilk or formula. The liquid can heat unevenly, and high heat can destroy nutrients. And microwaves are unpredictable. It's too easy to heat milk too high and burn baby's tongue. But you can use a microwave for quick heating; just don't put the bottle in it. This is a trick I learned from the nurses in the the neonatal intensive care unit. What you do is put your bottle into water that has been nuked.

The hospital used a Styrofoam cup; I used a coffee mug at home. Fill the cup about a quarter to a half full of water (you don't want it completely full, or it will spill when you put the baby bottle in it). Zap it for one minute on high. Then put your bottle filled with breastmilk or formula in the water and leave it in for about a minute. At the one-minute mark, refrigerated breastmilk or formula will be at about room temperature. Leave it in a bit longer for a warmer bottle. Gwynne

A good while back I saw a TV investigative program addressing just the plastics issue and I researched it a little more on the internet, with little success. It is basically the same thing about most plastics. The ones that were more harmful--according to the program--because they released small amount of some cancer causing chemical, which in the case of baby bottles would basically build up over time in the body, as the baby ingesting the liquid. I don't recall all the specifics of it, but essentially they said that the hard, clear plastics bottles were the ones that released the chemical and that the more pliable, colored bottles (like the tinted ones from Gerber) are safer. I emailed the Avent people requesting an explanation on these findings and they said that they were not aware that their bottles posed any risk whatsoever, and that their bottles are safe, despite the presence of PVC in the plastics of their bottles. In fact if you check on their website they actually say that their bottles are made with PVC. I simply refused to believe them and decided to go with the other bottles as well as not using them in the microwave. As a precaution though I suggest you not microwave any plastics in the microwave. It's better to side on caution than take unnecessary risks, especially when it involved your child. yanneth
Hi. I have an Avent. I was told never to microwave it. I know that microwaving will destroy the properties in breast milk. I'm not sure if that is the only reason not to microwave, or if it is bc of the plastic. J

Burned popcorn smell in microwave

June 2002

We recently burned (*SERIOUSLY* burned)a bag of microwave popcorn in our microwave, and can't get the smell (or yellow color) to go away. We've tried various cleaning supplies, baking soda, leaving it open for long stretches, etc. (and we've checked the website for ideas). Nothing seems to work - and after all of our efforts, the smell is still pretty strong when we open the door. Anyone have any ideas??

A couple of years back, we had a turkey spoil (very seriously) in our freezer while we were gone on vacation -- and had a similar problem with a smell we couldn't get rid of. The solution -- recommended by Amana -- that finally reduced the smell to tolerable levels, such that baking soda eventually cleared it up, was to pack the refrigerator/freezer full of crumpled newspaper and charcoal briquets, shut it up, and leave it for a few days. Sounds weird, but was remarkably effective. I wonder if something similar might work for you? Karen
Sorry to say that the only thing that works is time. We had a situation much like yours, and it took months to get rid of the smell and yellow coloring. We kept finding the coloring in various places, like under the sink where the popcorn bag had been tossed into the garbage. Now I use my air popper. jamie